1. Technical Field
The present invention concerns a clock, driven by a mechanical, electrical or electronic motor, with analog and unambiguous 24 hour display.
2. Description of the Related Art
Several clocks with an analog and unambiguous 24 hour display are known, for instance from DE 267 810 (D1), U.S. Pat. No. 5,696,740 (D2), WO 91/03774 (D3).
Both in D1 and in D2 the 24 hour unambiguity is obtained by means of two concentric number scales each of 12 hours, where the first 12 hour group comprises the times from 0-12 o""clock, the second the time from 12-24 o""clock. On the transfer from one scale to the other the hour hand always changes its position in an abrupt manner; it either travels outwards or is shortened.
In D3 the unambiguity of the display of the hours is addressed similarly in that two concentric 12-hour scales are arranged on the dial, at the same time however a transparent disc is present which has a period of revolution of 24 hours andxe2x80x94in one embodimentxe2x80x94has two semicircular shaped covers, which cover the nonapplicable hour values.
Further documents though not under consideration herexe2x80x94(i.e. DE 33 05 414 and DE 40 376 57) show clocks with so-called pseudo-analog presentation, where using electronic auxiliary means, such as LEDs and liquid crystal displays, an unambiguous 24-hour display is, created.
The arrangements published in D1 and D2 for the changing of the length of the hour hand require either additional energy from the clock motor for tensioning a spring (D1) or an additional source of energy (D2). The solution proposed in D3 shows the hours at all times of the day and night on two semi circles of different radius. Neither in terms of technical producibility nor in market acceptance were these solutions able to succeed.
Although it would be possible with the means described, the transfer from one scale to the to the other was never chosen to be other than at midday and midnight.
Further, clocks have become known, which have noncircular scales, such as for instance in DE 196 41 885 (D4), DE 299 03 950 (D5) and DE 299 34 451 D6). Whilst in D4 an hour indicating element is moved on any desired curve as a guiding element, in D5 the indicating element is guided on cycloids, which are generated by a four joint drive, by means of an additional gear wheel, means are described here to move the aforesaid indicating element on non-circular tracks, but a 24-hour indicator of an unambiguous nature is not published therein.
It is therefore the aim of the present invention to move the hour marking indicating elementxe2x80x94whether this is the hour hand or a clear and unmistakable elementxe2x80x94on a track of this construction, which permits an unambiguous arrangement of the positions of the indicating element during the 24-hour passage of the day and so by its position effects a conspicuous difference between the daytime and night-time hours without the need to alter the customary angular positions of the indicator.